The present invention relates to hydraulic pressure transformers, and, more particularly, to hydraulic pressure transformers having a rotor within an opening.
Hydraulic pressure transformers are used to transform an input flow of hydraulic fluid at a first flow rate and pressure to an output flow of hydraulic fluid at a second flow rate and pressure. The output flow rate and pressure are variable to provide a variable output flow and/or a variable output pressure for use with a specific application, such as a hydrostatic transmission.
Conventional hydraulic pressure transformers may have a housing with a rotatable barrel and a movable port plate disposed therein. The port plate has three arcuate slots which selectively interconnect a plurality of ports in the housing with a plurality of cylinders in the barrel upon rotation of the barrel during use. The relative position between the slots in the port plate and the ports in the housing define the output pressure from the hydraulic pressure transformer.
Examples of hydraulic pressure transformers as described above are disclosed in U.S. Pat. No. 5,878,649 (Raab), issued Mar. 9, 1999 and assigned to the assignee of the present invention; and PCT Document No. PCT/NL97/00084 (Achten), published Aug. 28, 1997.
It is also known to provide a hydraulic pressure transformer with a port block instead of a port plate between the housing and barrel. The port block has a spherical surface on each end thereof which abuts a complimentary spherical surface on the housing and barrel, respectively. The spherical surfaces at each end of the port block allow slight tipping or tilting between the housing, port block and barrel, while at the same time maintaining a substantially sealed relationship therebetween.
Although effective during use, hydraulic pressure transformers having a rotatable barrel and a plurality of axially extending cylinders as described above tend to be relatively complex and expensive to manufacture.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention, a hydraulic pressure transformer for the conversion of an input hydraulic power to an output hydraulic power comprises a cam block including a cam opening defining a pump section and a motor section. The pump section includes at least one pump inlet port and at least one pump outlet port. The motor section includes at least one motor inlet port and at least one motor outlet port. A rotor is disposed within the cam opening and is rotatable about an axis of rotation. The rotor includes a peripheral surface, a plurality of radially extending slots opening at the peripheral surface and a plurality of vanes respectively disposed in the slots. The rotor and/or cam block are movable relative to each other in at least one direction generally perpendicular to the axis of rotation.
In another aspect of the invention, a work machine comprises a frame; a hydraulic work unit; and a hydraulic pressure transformer for the conversion of an input hydraulic power to an output hydraulic power. The hydraulic pressure transformer includes a housing carried by the frame, and a cam block slidably disposed within the housing. The cam block includes a cam opening defining a pump section and a motor section. The pump section includes at least one pump inlet port and at least one pump outlet port. The motor section includes at least one motor inlet port and at least one motor outlet port. A rotor is disposed within the cam opening and is rotatable about an axis of rotation. The rotor includes a peripheral surface, a plurality of radially extending slots opening at the peripheral surface and a plurality of vanes respectively disposed in the slots. The rotor and/or cam block are movable relative to each other in at least one direction generally perpendicular to the axis of rotation.
In yet another aspect of the invention, a method of operating a hydraulic pressure transformer to convert an input hydraulic power to an output hydraulic power comprises the steps of: providing a cam block including a cam opening defining a pump section and a motor section, the pump section including at least one pump inlet port and at least one pump outlet port, the motor section including at least one motor inlet port and at least one motor outlet port; positioning a rotor within the cam opening, the rotor being rotatable about an axis of rotation, the rotor including a peripheral surface, a plurality of radially extending slots opening at the peripheral surface and a plurality of vanes respectively disposed in the slots; providing a hydraulic fluid supply tank fluidly connected with the pump inlet port, pump outlet port, motor inlet port and motor outlet port; rotating the rotor within the cam opening such that hydraulic fluid flows through each of the pump section and motor section; and moving the rotor and/or cam block relative to each other in at least one direction generally perpendicular to the axis of rotation.